1. Field of the Invention
The invention relates to a float-operated valve assembly for a water tank, more particularly to an improved float-operated valve assembly which minimizes component damage and which can accomplish faster and more effective blocking and unblocking of the water supply to the water tank than can the prior art.
2. Description of the Related Art
A float-operated valve assembly is usually installed in a water tank so as to control the supply of water thereto. A conventional float-operated valve assembly is shown in FIG. 1 to comprise a hollow valve housing (10). A horizontal inlet pipe (20) is connected to the valve housing (10) adjacent to a top end of the latter. The valve housing (10) has a pipe section (100) which is aligned with and which is opposite to the inlet pipe (20). A piston (11) is slidably disposed inside the pipe section (100). The valve housing (10) is further provided with a downwardly extending outlet pipe (12). One end of the piston (11) is provided with a plug (13) to block the inlet pipe (20). The piston (11) further has a bottom side formed with a notch (14). The pipe section (100) has a slot (100a) which is aligned with and which is longer than the notch (14), and a downwardly extending pivot seat (15) disposed adjacent to the slot (100a). A substantially V-shaped pivot arm (16) has an intermediate portion pivoted to the pivot seat (15). The pivot arm (16) has one end which extends through the slot (100a) and the notch (14) and which is provided with an enlarged head (17). The other end of the pivot arm (16) is connected to one end of a float arm (21). A float ball (22) is connected to the other end of the float arm (21).
The operation of the above described conventional float-operated valve assembly is as follows: The float ball (22) moves in response to a change in the water level inside the water tank (not shown). As the water level gradually decreases, the float ball (22) gradually moves downward, thus causing the pivot arm (16) to rotate in a clockwise direction and gradually shift the piston (11) away from the inlet pipe (20). The plug (13) eventually departs from the inlet pipe (20), thereby causing water to flow into the water tank. As the water level gradually increases, the float ball (22) gradually moves upward, thus causing the pivot arm (16) to rotate in a counterclockwise direction and gradually shift the piston (11) toward the inlet pipe (20). The plug (13) eventually blocks the inlet pipe (20), thereby stopping water flow into the water tank.
The drawbacks of the above-disclosed float-operated valve assembly are as follows:
1. Blocking of the inlet pipe (20) is a gradual process. The water level inside the water tank is in a rippling state as long as the plug (13) has not yet completely cut off the water supply to the water tank. The unstable movement of the float ball (22) due to the rippling of the water level can cause wearing of the plug (13) and can also cause wearing at the joint of the pivot arm (16) and the pivot seat (15).
2. Note that water pressure from the external water source opposes the blocking movement of the piston (11). The float ball (22) is used to overcome the force exerted by water pressure. This can cause damage at the link between the float arm (21) and the float ball (22) and at the link between the float arm (21) and the pivot arm (16).
3. Water flowing through the inlet pipe (20) may contain impurities (such as pieces of sandstones). Since the blocking action of the plug (13) is a gradual process, the impurities frequently rub against the plug (13) and may cause wearing of the same. Furthermore, the impurities may get stuck between the inlet pipe (20) and the plug (13), thereby preventing the latter from completely blocking the inlet pipe (20). The resulting water leakage can cause the water tank to overflow, thus leading to water wastage.
4. Effective blocking of the inlet pipe (20) is difficult to achieve since the different components of the conventional valve assembly are easily damaged.
5. The rate of water flow into the water tank is relatively slow since unblocking of the inlet pipe (20) is a gradual process.